public class builder {
    public static void main(String[] args) {
        //1.创建对象
        StringBuilder sb = new StringBuilder("abc");

        //2.添加功能
        sb.append("def");
        sb.append("ghi");
        sb.append("jkl");
        sb.append("mno");

        //3.反转功能
        sb.reverse();

        //4.获取长度
        int length = sb.length();
    }
}
